Softenable film material and method of using same



Sept. 17, 1963 w. s. MARX, JR., ET AL 3,104,175

SOFTENABLE FILM MATERIAL AND METHOD OF USING SAME Filed June 7. 1961 FIG.

Softenedflrea Sqtcnedbm afterllhpiny fiefomwzpuzg GMT SHEET WITH RESIN APPLY To SELECTED AREAS A COMPOSITION OF 1. SOLVENT 2. SOFTENER ALLOWSOLVENT To EVAPOEATE WIPE SHEET 7'0 Expos/5 AREAS BY Q WM aiiys United States Patent 3,104,175 SOFTENABLE FILM MATERIAL AND METHOD OF USING SAME Walter S. Marx, In, and Charles P. Collier, Santa Barbara, Califi, assignors to Printing Arts Research Laboratories, Inc, Santa Barbara, Calif., a corporation of Delaware Filed June 7, 1961, Ser. No. 115,285 7 Claims. (Cl. 117-10) This invention relates to a method of removing a hard, dry film from selected areas coated with that film and further relates to a film and a removing composition that are cooperatively constituted for use in said method.

Although this invention is not limited to any specific 7 use, it is particularly adapted for use in making color separations for producing printing plates to reproduce original colored art work. Most colored printing is presently made by photographically separating the colors of an original art work and making a separate photoengraving or lithographic printing plate for each of the three primary colors and for black. Photographic color separation is achieved with separation filters, however, the separation thus obtained is far from complete. True reproductions of color are rarely obtainable, .and good reproductions require hours of highly skilled hand work on the photographs or on the plates or costly photomechanical masking procedures.

By employing the material and the method of this invention, complete and true color separation can be made without the use of separation filters, hand corrections or masking. Briefly, this method employs a black and white art representation over which three hinged transparent or translucent overlays are placed. Each of the overlays is a transparent or translucent sheet upon which a hard adherent film containing transparent color is coated, and the overlays superimpose each other so that the black and white art representation is viewed through all three. Each overlay is colored with one of the three primary colors and all of the colors in the final art representation are produced from one or a combination of the primary colors. An artist working with this material obtains the ultimate design and colors that he desires by removing selected areas of the colors that he does not want so that the colored portion as viewed through the three sheets is obtained by a single color or combinations of remaining colors. I hus when employing overlays of red, yellow, and blue, where green is desired, as when an artist wants to color a representation of a lawn, it is obtained by removing red fromthe portion of the sheet superimposing the lawn representation and viewing the desired green area through both the blue and yellow sheets. When, for example, a blue sky area is desired, both the red and the yellow colored areas are removed from that section of the representation leaving only the blue. If the artist desires to put white clouds in the blue sky, he removes portions of the blue where the clouds are desired and the resultant clouds are viewed through the three sheets where all colors are removed and they appear white. When the representation, as viewed through the three overlays, is colored to the ar' tists satisfaction, the colors in the picture are quickly, completely and truly separated simply by separating the hinged overlays. With the colors thus separated, a separate color printing plate may be made for each color by employing virtually the same technique on each colored overlay as would be employed to make a black and white printing plate. Reproducing the colored representation is then accomplished by the known techniques of three color printing. This simple and complete isolation of the primary colors, by permitting the production of 3,104,175, Patented Sept. 17, 1963 screen separation negatives directly, effects large savings of time and material and in addition provides color reproduction of extremely high fidelity, particularly if the inks used in printing are matched to the color of the overlays used by the artist.

Previously, transparencies of this nature have been prepared by painting fast-drying transparent lacquers of different colors upon different overlay sheets and removing color from unwanted areas with a solvent for the lacquer. Due to smearing of the lacquer in such a process, it is virtually impossible to obtain narrow lines or v sharp outlines on an overlay. This method also requires the artist to work rapidly because highly volatile solvents must be usedto prevent unwanted residual effects. Sharp outlines and straight narrow lines were obtained by scratching the lacquer from the transparent overlay with a sharp scribe or other tool. Besides being difficult to work with, the sharp tools also are unsatisfactory because they require excessive time to scrape color from large areas.

It is an object of this invention to provide a solvent type resin composition that is capable of drying in the form of a solid, hard, light-transmitting film and capable of coacting with a specially constituted film remover in the form of a liquid which, when applied to the lacquer, cooperatively acts with that lacquer to provide a softened area that is easily removable simply by wiping it ofi. The lacquer is removed quickly and completely and with a sharply defined and abrupt line at the edges of areas where the remover is applied.

It is another object of this invention to constitute the film and film'remover to provide a softened area that remains soft and removable for long periods of time.

It is another object of this invention to provide a method for obtaining coated transparent sheet material item which selected local areas of the coating may beremoved. The film-removing liquid is not a solvent in the usual sense of that word. Rather, the film-removing liquid causes the film to soften and swell up and separate from the transparent sheet to which it was bonded so that it is no longer fixed to the transparent sheet and so that it is no longer fixed to adjacent areas of the film. The filmremoving material of this invention is preferably also constituted to provide the softened film with characteristics that render it non-cohesive with regard both to the transparent sheet material and to adjacent areas of the fi l-m so that it may be wiped oil without binding or sticking to any portion of the overlay.

The fi-lm and film-remover of this invention obtained their desirable properties by virtue of their cooperatively acting constituents which coact with each other to produce this novel and desirableeliect. I

The film of this invention that forms the hard coating on transparent sheet material comprises a resin or equivalent material which forms asolid, light-transmitting film. In addition, the film of this invention may contain other useful ingredients such astransparent dyes or colors, materials capable of absorbing ultraviolet radiant energy, plasticizers to impart a desirable degree of hardness and flexibility, wetting or surfactant. ingredients toproduce uniform coverage and consistency in the coating, and others.

The film-forming ingredient is a natural or synthetic resin or a resin-like compound that is soluble in a volatile organic solvent. The resins employed will be called solvent-type resins, and this term, as employed in this specification and the appended claims, is defined as a solid or plastic material which is soluble in a volatile solvent and which, when applied to a surface and upon 'ev'iaporation of the solvent, becomes a solid transparent or translucent film. A preferred solvent-type resin for use in this invention is ethyl cellulose which is a synthetic cellulose ether; however, other synthetic resins including polymeric derivatives of acrylic and methacrylic acids and certain vinyl acetate polymers maybe used. In addition, natural resins may be employed including damar gum, shellac, sandarac gum and others as well as a mixture of the above-mentioned materials. These materials are applied to the transparent sheets while in solution by brushing, spraying, rolling, printing, etc. Suitable solvents for use in applying the solvent-type resins to the sheet material include such organic solvents as glycol ethers, monohydric aliphatic alcohols, ethers, aliphatic cyclic or aromatic hydrocarbons, aldehydes, ketones and combinations of these.

When the transparent sheets are to be used for coloring artwork, they will contain a transparent dye or coloring to impart to them the desired color. Preferably, the dyes employed will be of the three primary colors and may be in varying intensities or shades of those colors. Of course other colors may also be employed where their use is indicated. As illustrative of suitable dyes, certain triphenyl methane dyes may be employed. In this class, a satisfactory red dye is para rosaniline acetate, a satisfactory yellow dye is .aurin and a satisfactory blue dye is Patent Blue. Xanthene coloring matters may also be employed, and as typical examples, Rhodamine may be employed as a red color and Fluorescein may be employed as a yellow color. Another satisfactory blue dye consists of a mixture of pentamethyl-benzyl-p-rosaniline (Methyl Violet) and phenyltetramethyl triamido-a- .naphthyldiphenyl carbinol hydrochloride (Victorial Blue), and another yellow dye may consist of p-dimethyl-amido azo'benzene (Methyl Yellow). A20 and diazo type dyes may also be employed. Since the dyes are employed only to contribute their color, suitable dyes, which maybe the primary colors or other colors, literally number in the hundreds, and the foregoing specific examples are intended only as a few operative examples which illustrate the invention rather than a limiting disclosure of suitable dyes.

For use in photographically preparing halftone negatives for printing plates, it may be desirable to include ultraviolet absorbing materials in the film-forming mixture, so that halftone screen patterns or dots may be removed from non-work areas of the negatives by an unscreened exposure to. ultraviolet light. Ultraviolet absorbers may be used in conjunction with colored sheets or they may be used in clear coatings for special photographic uses. Many such absorbers for ultraviolet radiation wave lengths are available and may be employed. By way of example, various Z-benzophenone compounds (2,4-dihydroxy-benzophenone; 2-hydroxy 4 methoxy-S- sulfo benzophenone, etc.)- may be employed as well as certain quinine compounds such as quinine, quinine bisulfite; antracine derivatives; coumarin derivatives such as benzyl beta methyl um-belliferone and 4-methyl-7-diethyl amino coumarin; nitro compounds such as picric acid paranitrophenol and 3,5-dinitro salicyclic acid.

It is contemplated that the transparent sheet material employed as the superimposed overlay sheets upon which the transparent color composition is applied will be any material that is suitably transparent, formable into sheets and dimensionally stable enough to retain adequate outline register of each color with others. Many materials are presently available such :as clear polyester sheets well known commercially as Mylar, produced by E. I. du Pont de Nemours & Co. (Inc), of Wilmington 98, Delaware, acrylic sheeting, polyethylene, vinyl polymers, urea formaldehydes, polystyrenes, unfilled phenol formaldehydes or even sheets of glass. The material used is preferably tough, and flexible but still enough to resist wrinkling or folding, resistant to staining when color coatings are applied and removed and unaffected by the films or solvents contained in the film-removing compositions.

The composition of the film may be regulated so that a film that is too hard or too soft is avoided. Plasticizers such as sulfonated lauryl alcohol, coconut oil, modified castor oil, phthalates and organic phosphates, and others, when employed in appropriate amounts, produce a film with the proper plasticity, that is one that will dry hard, but will not become brittle or crack. The film should be spread uniformly on the transparent sheet material thick enough to give a good color intensity but thin enough to be quickly permeated by the film remover. Films spread to have from about 0.005 to about 0.0001 ounce of solids per square foot have been found satisfactory.

The film-removing liquid of this invention comprises two primary components and may contain other ingredients to improve its utility. The. two primary components are a relatively volatile, active solvent for the film and a softening orswelling agent that causes the film to swell and prevents resetting of the film or adhesion to the sheet after the solvent evaporates. Although the filmremoving composition contains a solvent for the film, it does not produce the problems associated with removing the film with a solvent because all of the solvent evaporates before the film is removed. Therefore, smearing of the areas adjacent to the removed area does not occur. The solvent component of the film-removing composition places the film in solution temporarily to facilitate rapid combination of the film with the softening or swelling agent. The solvent component of the film-remover consists of a relatively volatile organic liquid that dissolves the film but not the transparent base sheet. Such liquids as volatile aromatic hydrocarbons, chlorinated aliphatic hydrocarbons, monohydric aliphatic or cyclic alcohols, ether alcohols, others, esters and ketones as well as mixtures of these may be used. After the film is combined with the softening or swe1ling agent, the relatively volatile solvent evaporates substantially completely prior to removing the film from the transparent sheet material. Therefore, when the softened fihn is removed as by wiping with a cloth, the fragments of removed softened film that come in contact with adjacent areas of the film do not cause dissolving or softening of those areas because no solvent is present. There is no need for haste in either applying the film-removing composition or in wiping film from the transparent sheet because the softened areas of the film remain in softened and removable condition for hours.

In addition to the active solvent and the softening or swelling agent, the fihn-removing composition may contain such substances as a lubricant which facilitates removal of the softened film from the transparent sheet and which prevents fragments of the softened film from sticking to the adjacent unsoftened areas of the film during removal. The lubricating component is preferably a non-drying compound such as coconut oil or other vegetable oils, animal oils, low aromatic content mineral oils, glycerides or fatty acid esters that are inert with respect to the film and base sheet material.

The softening agent employed in the film-remover is at most a limited solvent for the film. Its action is to interfere with the normal setting of the solvent-type resin by dispersing the film in it and by coating the flexible sheet material to prevent adhesion of the resin to the flexible sheet. Although the film is easily dispersible in the softening agent when the volatile solvent places it in sol ution, the softening agent is not a solvent, and if applied by itself little softening would occur, and that softening would require prolonged contact.

The softening or swelling agent is a relatively non-volatile organic material in which the combined film and the solvent are dispersible, but one having no adverse effect on the transparent sheet material, such as many of the commercially availablesurfactants. By way of illustration, softening and swelling agents such as sulfonated lauryl alcohol esters, commercially known as Triton GR-7 and Triton GR-S produced by Rohm and Haas Company, polyoxyethylene sorbitan monostearate which is commercially known as Tween 60 made by the Atlas Powder Company, sodium dioctyl sulfosuccinate which is commercially known as Alrowet D-65 made by Geigy Chemical Corporation, sulfonated aliphatic polyesters commercially known as Nekal WS-25, and nonyl phenoxy polyoxyethylene ethanol which is known as Igepal CO-630 which are products of the Antara Division of General Aniline Film Corporation, have all been found to produce excellent results. Good results have been also obtained employing as a softening or swelling agent such material as solid fatty acids, for example stearic acid and palmitic acid, as well as butyl stearate and triethylene glycol di-2-ethyl 'butynate and other materials having similar properties.

The film remover of this invention also advantageously may contain a protective colloid material such as polyvinyl pyrrolidone which is useful for entrappin-g or binding the dye in the softened film or fragments of the softened film to prevent them from sticking to or precipitating on the areas of the flexible sheet material from which film is being removed. It is also advantageous to employ a soluble dye or pigment in the film remover to make the liquid remover visible therefore facilitating the detailed application of the filmremover.

The solvent type resin is applied to the transparent base sheet material dissolved in a solvent so that when the solvent evaporates a hard, dry film or coating remains. The criteria for determining the quantity of solvent type resin in the solvent are whether or not enough resin is present to provide a stable dry coating and whether or not enough resin is available to be capable of holding the other ingredients in homogeneous dispersion. As hereinbetore stated, the solvent should contain sufiicient resin in solution to provide a dry film in an amount of from about 0.005 to about 00001 ounce per square foot of flexible sheet.

When ultraviolet absorbers are employed as ingredients of the film they will be present in concentrations to perform their function and those concentrations will vary depending on the absorptiv-ity of the specific absorptive compound and on the intensity and the duration of the anticipated exposure to ultraviolet energy. When ultraviolet absorbers are used, they generally will constitute from about 3% to about 50% by weight of the dry film.

Plasticizers, when used, will be present in concentrations to provide the dry film with the proper degree of flexibility and will usually constitute from about 0.25% to about 10% by weight of the dry film.

The criteria for determining the quantity of relatively volatile solvent in the film-removing composition are that enough solvent must be present to provide a liquid filmremoving composition, to maintain the softening or swelling ingredient in homogeneous dispersion, and to dissolve rapidly the film in local areas where remover is applied. The quantity of volatile solvent will vary widely depending upon what specific solvent is used, upon what specific film material must be dissolved, upon the thickness of that film and upon the amount of softening component and other components that must be maintained in homogeneous dispersion. Generally, the volatile solvent will constitute from about 25% to about 90% by weight of the film-removing composition.

The softening or swelling component of the film-removing composition must be present in sufficient quantity to soften the coating over the area to which it is applied, and to maintain the coating disassociated from the flexible sheet, and therefore removable, after the solvent is evaporated. Generally, the softening component constitutes from about 10% to about 75% by weight of the film-removing composition.

When the film-removing composition includes a lubricant component, it is usually present in concentrations of from about 5% to about 25% by weight of the filmunaffected, and

removing composition and when a protective colloid is employed it preferably constitutes up to about 10% by weight of the total composition. Since the coloring matter contributes only visibility to the film-removing corn-i position, a quantity sufiicient for this purpose is employed.

The accompanying drawings are provided to illustrate one embodiment of this invention.

FIG. 1 is a sectional view of a base sheet coated with a film, pant of said film having been removed, part of said film having been softened in accordance with this invention to be removable, and part of said film being FIG. 2 is a schematic diagram illustrating sequentially the steps which may be employed in the practice of one embodiment of this invention.

Following is an example which is presented to illustrate one presently preferred embodiment of this invention and it is intended as being illustrative rather than limiting on the scope of the invention.

A solution of 800 grams of ethyl cellulose employed as a solvent type resin, in a solvent consisting of 4850 grams of methyl ethyl ketone, 3360 grams of ethylene glycol ethyl ether and 2900 grams of toluene was prepared. Afiter complete solution was obtained 75 grams of sulfonated lauryl alcohol ester 'was also dissolved in the solvent as a plasticizer for the ultimate film and 100 grams of azosol Fast Red BE dye and 33 grams of azosol Fast Red 3BA dye were employed as red dyes,-

both of which are products of the General Dyestulf Co. Azosol Fast Red BE is identified by color index No. 12715 and azosol Fast Red 3BA by color index Nos. 45170 and 16260, said color index numbers being assigned by the American Association of Tex-tile Chemists and Colorists to identify both the color and the chemical composition of recognized coloring materials. As ultraviolet absorbers, 270 grams of 4-methyl-7-diethylamino coumarin and 400 grams of 2-hydroxy-3,5-dichloro benzophenone were also dissolved in the solvent. The homogeneous liquid dispersion formed as described was uniformly gravure-printed on a sheet of clear Mylar and within a few minutes the solvents evaporated leaving a uniform coating of transparent red-colored solvent-type resin over the entire area of the Mylar sheet.

A film-removing composition was made by co-iningling 150 grams of toluene, 450 grams of isopropanol, 200 grams of Triton GR7 (sulfonated lauryl alcohol ester), 150 grams of coconut oil, 50 grams of polyvinyl pyrrolidone and a few grams of Victoria Blue dye to provide enough deep blue color to the composition to make it readily visible even when spread-in a thin layer.

The flexible sheet coated with solvent-type resin, when dry, was like a lacquer being resistant-to water, abrasion,

. etc. It maintained permanent color, texture and dimensional stability.

The film-removing composition which may be characterized as an artists drawing fluid was applied locally with an artists brush to the sheet thus prepared by writing the Words Paint it on Wipe it off! thereon and the film-removing composition spread smoothly over the coated sheet covering only the areas where it was applied with the artists brush. Within several seconds a change in the texture of the resin coating where the removing composition was applied could be observed and within 15 seconds the area of the coating beneath the remover was considerably altered. By the time 15 seconds had elapsed, the volatile solvent component of the film-removing composition had evaporated and the film-removing composition that remained on the film had a pasty appearance. The sheet was then rubbed lightly with a dry cloth, and in the areas where filmremoving composition was applied, the red-colored coating of resin was completely and abruptly removed exposing the clear plastic Mylar sheet beneath. The boundary where the resin coating was removed was extremely 7 sharp in that there was no raggedness or smearing. When the sheet thus prepared was laid on a white sheet of paper, the words Paint it on Wipe it off! appeared in white against a red background.

In this specification and the appended claims, several terms are employed which are intended herein to have a strict definition. The terms dispersion or dispersible as used herein are defined to mean any homogeneous distribution in a liquid phase or anything capable of being homogeneously distributed in a liquid phase and these terms are intended to include solutions, emulsions and colloidal suspensions as well as the capability of forming the same.

The term relatively volatile as related to a solvent is herein defined as describing a material that will evaporate in less than about two minutes when spread as a thin film. However, the same material, for example, isopropanol, may not evaporate over a considerably longer period when in the form of a compact mass such as when confined in a bottle, in a deep pool or absorbed in the hairs of a paint brush.

The term relatively non-volatile is defined, as used herein, to describe a material that will not completely evaporate in a period of one hour under ordinary conditions of temperature and at ordinary room conditions even when spread as a thin film from a paint brush. It is not intended that this definition should be strictly interpreted under unnatural conditions such as when the non-volatile material is spread as a film only several molecules thick or subjected to strong air currents, steam or other conditions that greatly accelerate evaporation. The term transparent is intended to include, in addition to absolutely clear material, translucent sheet material such as sheets with a matte or frosted finish which are not clear, but which transmit light and can have lines or other representations distinguished through them when they are in contact with the surface on which the lines are drawn.

Having thus described the invention, what is claimed 1. The method of obtaining a coated sheet having a selected area from which the coating is absent which comprises applying a solution of solvent-type resin to a supporting sheet, drying said solution .to obtain a dry coating of said resin on said sheet, covering said selected area with a film-removing liquid comprising a homogeneous dispersion of a relatively volatile solvent for said resin and a relatively non-volatile softening agent which is inert with respect to said supporting sheet and in which said resin is dispersible, maintaining said selected areas covered with said removing liquid until said relatively volatile solvent evaporates and wiping at least the area covered with said removing liquid to remove said resin and to expose said supporting sheet.

2. The method of creating an image on a preformed base sheet having a solvent-type resin film adhering thereto by removing a part of said film, said film including a member selected from the group consisting of a colorant, an ultraviolet absorbent and mixtures thereof,

the steps comprising: applying an artists drawing fluid to a selected portion of said film, said fluid comprising a homogeneous dispersion of a relatively volatile solvent for said film and a relatively non-volatile softening agent for said film, dispersing said portion of the film in said softening agent, maintaining said selected portion covered with said artists fluid until the relatively volatile solvent volatilizes, and then wiping the portion initially covered with the artists drawing fluid to remove said portion and to expose said base sheet.

3. The method of claim 2 in which the artists drawing fluid includes a protective colloid in an amount up to about 10 percent by weight thereof.

4. The method of claim 2 in which the solvent-type resin is ethyl cellulose.

5. The method of claim 2 in which the artists drawing fluid includes a lubricant.

6. The method of claim 5 in which the artists drawing fluid includes coloring matter.

7. The method of creating an image on a preformed base sheet having a solvent-type resin film adhering thereto by removing a part of said film, said film including a member selected from the group consisting of a colorant, an ultraviolet absorbent and mixtures thereof the steps comprising: applying an artists drawing fluid to a selected portion of said film, said fluid comprising a homogeneous dispersion of a relatively volatile solvent for said film and a relatively non-volatile softening agent in which said film is dispersible, the solvent being present in an amount of from about 25 to about 90 percent by weight, said agentbeing present in an amount of from about 75 to about 10 percent by weight, said fluid further including a lubricant in an amount of from about 5 to about 25 percent by weight, a protective colloid in an amount up to about 10 percent by weight, and coloring matter, maintaining said selected portion covered with said artists drawing fluid while the relatively volatile solvent evaporates and while said film becomes dispersed in said softening agent, and then wiping the portion covered with the artists drawing fluid to remove said portion and to expose said base sheet.

References Cited in the file of this patent UNITED STATES PATENTS 799,609 Ludwig Sept. 12, 1905 1,408,816 McClellan Mar. 7, 1922 r 1,646,907 Freund Oct. 25, 1927 2,312,088 Fleming Feb. 23, 1943 2,342,885 Morgan Feb. 29, 1944 2,435,239 Schub Feb. 3, 1948 2,671,758 Vinograd et al Mar. 9, 1954 2,996,397 Secker Aug. 15, 1961 OTHER REFERENCES Bennett, Concise Chemical and Technical Dictionary, Chemical Publishing Co., Inc., 1947, p. 866.

Lange, Handbook of Chemistry, 9th ed., Handbook Publishers Inc., 1956, p. 677. 

1. THE METHOD OF OBTAINING A COATED SHEET HAVING A SELECTED AREA FROM WHICH THE COATING IS ABSENT WHICH COMPRISES APPLYING A SOLUTION OF SOLVENT-TYPE RESIN TO A SUPPORTING SHEET, DRYING SAID SOLUTION TO OBTAIN A DRY COATINGG OF SAID RESIN ON SAID SHEET, COVERING SAID SELECTED AREA WITH A FILM-REMOVING LIQUID COMPRISING A HOMOGENEOUS DISPERSION OF A RELATIVELY VOLTATILE SOLVENT FOR SAID RRESIN AND A RELATIVELY NON-VOLTTALITE SOFTENING AGENT WHICH IS INERT WITH RESPECT TO SAID SUPPORTING SHEET AND IN WHICH SAID RESIN IS DISPERSIBLE, MAINTAINING SAID SELECTED AREA COVERED WITH SAID REMOVING LIQUID UNTIL SAID RELATIVELY VOLATILE SOLVENT EVAPORATES AND WIPING AT LEAST THE AREA COVERED WITH SAID REMOVING LIQUID TO REMOVE SAID RESIN AND TO EXPOSE SAID SUPPORTING SHEET, 